In dental treatments, dental curable compositions comprising polymerizable monomers, inorganic fillers and polymerization initiators have been widely used. These are generally called dental composite resins and utilized for various uses such as direct restorative materials for tooth defective parts due to dental caries, etc., dental crown prosthesis restorative materials such as inlays, crowns, and bridges, materials for constructing anchor tooth for dental crown defective parts, block materials for dental CAD/CAM, etc.
Dental restorations using the dental composite resins have a long history, and their ranges of use have been expanded. However, the mechanical properties of the dental composite resins are not still enough, and their actual condition is that an application to a part having high dental occlusion stress in an oral cavity (e.g., for dental crown materials for molar teeth) is restricted.
Furthermore, mechanical strength degradation of the dental composite resins in an oral cavity environment is regarded as problematic in recent years. Therefore, a development of the dental composite resins having the durability capable of maintaining mechanical strength over a long period of time under the severe environment in an oral cavity, has been desired.
Various characteristics needed for the dental composite resins are greatly affected to the molecular structures or combination composition of polymerizable monomers. The technological background of the polymerizable monomers which have been used for the dental composite resins is shown below.
In many cases, polyfunctional radical polymerizable (meth)acrylates are used as the polymerizable monomers to be used for the dental composite resins from viewpoints of safety in the body, the mechanical strength or abrasion wear resistance of cured products, etc. Combinations of 2,2-bis(4-(2-hydroxy-3-methacryloxypropoxy)phenyl)propane (hereinafter referred to as Bis-GMA), 1,6-bis(methacrylethyloxycarbonylamino)2,2,4-trimethylhexane (hereinafter referred to as UDMA), triethylene glycol dimethacrylate (hereinafter referred to as TEGDMA) are widely used as compositions of general polymerizable monomers. Dental composite resins which use these polymerizable monomers can be used without any problems as long as their application cases are limited. However, in the case that their application is expanded to a site to be subjected to high stress, such as a molar tooth, destruction and chipping of the dental composite resins had occurred since their mechanical strength was not enough.
Patent Documents 1 to 3 suggest methods for enhancing the mechanical strength of dental composite resins by using polymerizable monomers substituted for Bis-GMA or UDMA. However, even for dental composite resins of those inventions, their mechanical strength was not enough and there was a need for an improvement.
On the other hand, methods for considerably enhancing the mechanical strength of dental composite resins has been proposed by utilizing the hydrogen bonds between urethane bonds and hydroxyl groups included in polymerizable monomers. In Non-patent Document 1, a method for enhancing the mechanical strength of dental composite resins is proposed by using polymerizable monomers having urethane bonds, and monofunctional polymerizable monomers having carboxyl groups. However, although dental composite resins of this document conferred high mechanical strength to the dental composite resins, their aged deterioration in a water immersion environment was intense, and thereby there was a problem in their durability in an oral cavity environment.
Patent Document 4 proposes a method for enhancing the mechanical strength of dental composite resins by using polymerizable monomers having urethane bonds and polymerizable monomers having hydroxyl groups. However, although dental composite resins of this document conferred high mechanical strength to the dental composite resins, their aged deterioration under a water immersion environment was also intense, and thereby there was a problem in their durability in an oral cavity environment.